Tragic Flaw
by The WGPM
Summary: Surprise third installment of the MfEO series! (Does not act as a standalone; first two are required.) It's Phineas and Isabella's last ever day of summer vacation, and it appears both have spontaneously become perfect again. Now they must face one of their toughest choices yet: stay perfect, or stay together? (Phinabella AU One-shot)


**Hey hey hey! Another year down in the MfEO books! October 21 was the day the first one came out in 2014, then 2015 brought the last chapter and epilogue of _Misspent_ , along with the first story rewrite; 2016's bringing this. Whether or not you were expecting a threequel (is that what comes after sequel?), here it is. That being said, please please PLEASE make sure you have read the first two books before this, _Made for Each Other_ and _Misspent_. Or else you will be VERY confused. So very confused.**

 **Anywho, this one will just be a one-shot. The whole plot plays out in five thousand words, so buckle it up.**

 **I don't own Phineas and Ferb, but I do own the MfEO series. Which you must be familiar with if you are reading this.**

 **Just as a reminder, this takes place two weeks after the MfEO version of "Act Your Age," which is found in the epilogue of _Misspent_. (As such, Phineas and the gang are 21 years old.)**

* * *

For the first time in years, there was peace.

There had been peace before, of course, in various places between certain groups of people. All along there had been at least one place in the world where calmness and serenity flourished.

But the nature of mankind made the opposite also true. Somewhere there was fighting and hatred in the world. Even in little pieces, it was always there.

This morning things were different. No one knew it, but for a full sixty seconds before the break of seven AM in the Tri-State Area, there was none. No country had any quarrels with another. All competition was suspended. No younger siblings pulled their older sibling's hair, and no older siblings took revenge. Even in the densest jungles where man had never stepped, and in the blackest depths of the ocean where the water was cold and heavy, no animal feasted on another and no bacterium took life that was not their own. For a full sixty seconds, there was peace.

Then Phineas' alarm clock rang.

The young man shook himself awake. He shook the sleep out of his eyes and he shook the flatness out of his pillow. He shook the alarm off. Today he was shaking.

Today was the first day of the rest of his life.

Today he was going to college.

He could never had gotten ready fast enough. Orange shirt and jeans, on. Teeth, brushed and flossed. Hair, combed. Showered, yes. Breakfast, two sad pieces of cinnamon toast. But he cared not. The cinnamon was sweet and the butter spread and melted evenly.

Tri-State State was only about two hours' driving time away, but he had a world of other things to do today - his last ever day of summer vacation.

It was going to have to be perfect.

* * *

Isabella's morning was somehow less hectic. She woke up with the knowledge that she would see Phineas again today. That was that. Time to college.

That was something she did at her own pace. It was a fast one, but it was hers and she was okay with it.

It was the last day before classes technically began, but being a freshman RA was demanding enough to get her there a couple weeks early. She was just about ready to begin by now, though; a few more things to do and this year would be hers. By her expectations, today was going to be easy.

Instinctively she glanced at the clock. By now it was almost nine. He would be here in...

No. She decided not to think about that. She had gotten the dorm ready yesterday; there was no need to focus on his arrival until it came.

But telling herself that was all it took for something overjoyed to bubble up inside her. It did not show as much as she felt it, but it did cause a large grin to grow across her lips. Within seconds she was the picture of someone who knew they were going to win the lottery at some point and was calmly exuberant that it was happening now.

She gave it a second or two, then inhaled deeply and moved her thoughts elsewhere. Easy as it would be, today would be a big day.

* * *

Phineas grunted as he tied the last of his luggage onto the car. He thought he had compensated for more storage room in the design; oh well. He saw the beauty in traveling heavy.

Done. He hit his waist at the right; keys were in his pocket, everything was ready to go when he was. That would be in a few hours.

He took a moment for sentimentality now. He could clearly see her house from here, vacant now except for her hardworking parents. Then there was his house. Ferb was already in England and Candace was living across town with Jeremy now. Baljeet would begin teaching soon, and there was no way he could be reached for a project the day before that started. And Buford... was probably sleeping in.

Then there were Mom and Dad. Mom, like Baljeet, was always busy the day before school started, this year for the same reason. He would seek out Dad, then, but for the past two weeks he had been acting completely mad. Phineas tried to reason his experience with Isabella that day had nothing to do with it.

So today was going to be all to himself. A shame, he figured, but there was nothing to do about it. Besides, today's project was going to be a personal one, and he would rather work alone this time.

It was during these thoughts that he heard the beeps and looked up. A familiar yellow sports car had just pulled up, baring even more familiar faces.

Phineas lit up and waved them over. "Hey! What's goin' on, guys?"

"What's going on with us?" Candace repeated, stepping out of the passenger door. "What's going on with _you?_ "

"Phineas," Vanessa greeted. "All packed up already?"

"Yeah." He gave Candace a hug and turned his attention down to Amanda, affectionately messing up the little girl's hair. "What am I if not prepared?"

"True that," Vanessa agreed, looking up and down his vehicle. "Anyway, we can't stay; but we wanted at least to stop by to see you off."

"Well - sure! Come on in."

He led them inside. "Mom, Dad - Candace and Vanessa are here."

"And Amanda," the young girl added, but at that point Lawrence was already in saying his hullos.

"You two!" The man jabbed.

"Three," corrected Amanda.

"Good to see you again! Tell me dear, how is Jeremy?"

"Wonderful," Candace responded without a beat. "He says hi, by the way. Wanted to come but, you know, work."

"Good to hear it. And Vanessa? How are things at home?"

"The best it's been in a while," she responded with a smile.

"Neato. Say, can either of you drive a four-wheeler?" With this, Lawrence withdrew a helmet; Phineas intervened.

"Um, they're just here to say hi, you know. Right? Not really time for anything exciting."

He could tell they wished he was faking that. "Actually, yeah," Vanessa agreed. She sent Phineas a look. Since when was his stepfather into off-roading? The young man shrugged in response.

Meanwhile, Candace was looking around the room for anything out of place. Only Vanessa noticed, but to her it was obvious Candace was not ready to leave at least one of the boys un-busted before they left.

Everyone knew she had calmed down about that, but old habits die hard, as they say.

* * *

Somehow Isabella found herself totally finished with each and every obligation she had before tomorrow, and now had a few hours to herself before - before the thing happened.

Now she was laying face-up on her bed, arms above her head, lost in thought. Inevitably they turned to him, and she had no reason to fight it now. It had only been two weeks, for sure, but two weeks in Phineas and Ferb time was equivalent to the eventfulness of seven to eight months. When he arrived, there would be seven to eight months of catching up to do, and it already felt like she had been missing him for seven to eight months.

Despite this, she remembered two weeks ago like it happened five minutes ago. Now everyone knew. It had been eleven long years since she had been Isealia, long enough for sure for the secret to fade to irrelevance. They deemed it safe to tell everyone and now everyone knew.

And Phineas knew about _her_.

 _Her_ imperfection. It had taken him long enough, but in a way she understood: he was a busy man with a lot on his mind, even as a child.

But even after learning that, he stayed with her and decided to go to her school. He sought her out for everything she had been - imperfect, enamored, and hugely a secret.

There was something special about this. And in this moment the exhausted girl closed her eyes, smiled slightly, and drifted out of consciousness for a while.

...

The peace from this morning returned fully, at least for Isabella. On the outside she was not moving at all. She was breathing, but subtly enough that her chest was stationary, and her face stayed fixed in place, framed by the pink lace on her pillow. She felt nothing because she was asleep, but inside her something had started happening.

It was something she had not experienced for eleven years. She was changing.

Isabella's poor heart was working harder than ever to keep up with it, but it was done shortly.

Her breaths even, Isabella's eyes slid open. The world looked no different to her, yet she looked different to the world.

She did not even know anything happened, but she did feel something distantly, distinctly familiar in her mind.

The first thing she did after standing up was removing her hair bow and placing it gently on the nightstand beside her. The second thing was slipping into a stark white blouse and equally white slacks and flats.

* * *

Phineas was regretful that Candace and Vanessa could not stay longer, but he was glad now that they did not have to see him like this.

It had just sank in: college was starting in less than twenty-four hours. He had heard things about what was in store, and like most of the students entering in, he was having mixed feelings.

But at least he would still have her, was the thought that tipped these feelings into the excited side of the spectrum.

And to think he had only seen her downwards of ten minutes after finding out she was just like him. Wow.

He still had a hard time comprehending it - she had done nothing he was aware of in the past eleven years that was less than perfect. She was everything he expected the best human to be. And he should know! Of all people, who but those two would be the best to recognize perfection?

Wow.

And now the next part of his life was about to start with no one he knew but her. Beautiful, caring, fatally-flawed her.

 _Wow_.

Phineas was not doing anything while thinking of all this. The extent of his external actions was breathing and blinking. Right now he was sitting at his desk in his bedroom - it was so empty now that everything was in the car - elbows propping up folded hands propping up a constantly-busy head.

And in his head, something began changing.

* * *

Before Isabella could do anything else, her phone rang. She did not keep the caller waiting.

"Hello, Gretchen," she greeted, already knowing who it was.

"Hey Isabella! How's it going? Big day ahead, huh?"

"Things are good here," the woman responded. "There is a lot to look forward to."

"I'm sure."

Isabella smiled. "Are you doing well?"

"Great. Stressed. But you'll get used to it fine."

"I concur. I haven't spoke with Irving lately; is everything good with him too?"

"Oh, yeah. He got a car."

"Good for him."

There was a slight silence. "Anyway, I just called to ensure you're all ready for tomorrow," Gretchen concluded. "And Irving says hi."

"Inform him of my returned salutations, then."

Isabella thought nothing of it, but that response had to sink in for Gretchen. "Wow. Are you really okay? I haven't heard you speak that eloquently in years. College, huh?"

"It truly is a time of change," she agreed, but Gretchen was still confused. "In fact, your timing in making this call is impeccable. It is apparent to me that _I_ have recently changed: I sense your suspicions and must confirm them. While impossible to identify the exact reason-" she whispered the rest. "-I have returned to the state of perfection available to me as a child."

Gretchen's small mouth hung slightly open; she pushed her glasses up. "Are really?" She blurted, then choked on her words. English momentarily escaped her.

"I am telling you not so that you may act as my messenger, but as my confidante. As of now, I find it unwise to advertise this development, but I will keep you posted."

Gretchen swallowed. "Of course I'll be your aide again," she interpreted. "But what about Phineas? Reckon he is experiencing the same?"

Isabella had already considered that. "If so, it would be for the same reason. I have a proposal of what that might be, but delineating it would involve breaking a promise of confidentiality I made with him."

"I understand," Gretchen said, although she was aware Isabella already knew. "Should I call him?"

"If he has not underwent the same changes, he will be leaving in a few hours. If he has, he may be wondering the same as we are and interrogate you on the subject. Are you prepared to approach such a situation without betraying my trust?"

Gretchen thought for a bit. "No. Not if Phineas is perfect again and really wants to know."

"I value your honesty," Isabella responded. "From there, then, I trust your insight to decide what is the right thing to do."

At that, Gretchen smiled. "Thank you very much. Well, I might as well let you go. You're a busy girl about now, aren't you?"

"That would be an accurate assumption, yes," she said. "Do yourself well until we speak again."

"Likewise for yourself," returned Gretchen. "So long." She hung up.

Isabella thought of her idea - it was the only explanation. It also meant that Phineas's arrival would erase her newfound state of being, and his if he had it too. She now saw herself presented with a choice: stay perfect, or stay with him.

Isabella replaced her phone, then appraised the room. There were pathogens in it; she had work to do.

* * *

Phineas knew better than to step into the spotlight that was the outside in Danville, wearing the signature white clothing of last decade's Perfeneas. The resemblance would reveal to anyone still unaware they were the same person, and the people who did know would find out in a second what was happening.

By 'today was going to be perfect', Phineas did not mean 'today I am going to be perfect.'

But that was the hand he was dealt, and by golly he was going to make the most of it.

He set to work quickly - there was only so much time left before he had to leave if he was to make it on time. And while he was thinking of leaving, he could not go in a car that was powered by this fuel. In five minutes he discovered and acquired an alternative energy source and loaded it into his car.

Just as quickly he was finished cleaning up his house - helping his parents and not intending to leave them with his mess. Time for the real work.

The last time he was on the moon, he chiseled a sample of rock from its surface. This sample he cleaned, cut, polished, and placed in a superheater he had a few miles below the ground. He forced a few tons of pressure on it and observed for a while, just to see what would happen. This took most of five hours.

All throughout it Phineas was thinking of Isabella - what else, the day he would see her after this long, and continue seeing her daily again. Just like in his childhood as Phineas Flynn of Danville, Isabella García-Shapiro would be a constant - but now it would be different. She would be the only one. No Ferb, no Buford and Baljeet, no Mom and Dad, not even Perry.

He was perfect again, now. The question was whether she was too. He just learned it recently, but the last time his state of perfection changed so did hers; but one time eleven years ago was too small a sample size to be reliable.

Back then - and this he knew since it happened - the change was brought on by the introduction of joy to his robotic and objective mind. The explanation he was thinking up now was that the emotional desire starting then had just been fulfilled today.

Thank you, Isabella.

His project was finished and pocketed now, and it was time to leave.

"Phineas, it's three. Are you all-"

Right on queue. Linda was standing in the doorway to outside, a look of concerned confusion on her face. "I - like that outfit... trying something new?"

Phineas's face gave sympathy. "Hardly, discounting the last decade. I find it appropriate to return to the look of a younger Phineas today."

Linda was unsure why, but never questioned her son, and left it at that. "Well, I think you'd better get going if you want to get to school on time. Come here."

She held her arms wide, and her son complied. "I love you, Phineas. I'm so, so proud of everything you've done."

Phineas was gracious, but not vain. "I couldn't have done any of it without you. Thank you so much for being my mother."

Linda squeezed him tighter and tears appeared, but she decided not to hog him from his father, who was standing nearby.

"You too, Dad. I couldn't have asked for a better family."

The three of them smiled bittersweet smiles. "Now, go out there and show them what you can do," Lawrence demanded, putting a hand on his stepson's shoulder.

Phineas beamed, said his goodbyes, and did as he was told.

* * *

Fortunately enough, Isabella was between tasks when Gretchen's second call came through.

"Isabella, I need to talk to you about something."

She could tell Gretchen was urgent. "I'm listening. What is it?"

"You-you're still perfect, right?"

"As far as I am aware, yes."

"Ascensión found me. My old colleague from Mexico? She's up here and thirsty for blood."

Isabella remained calm, but surprised. "Who's?"

"Yours, or else I wouldn't be calling you."

Isabella knew that the second part was not true, but did not correct her. "What did she want to do, then?"

Gretchen was panicking. "She just wants to find you. I don't know how she found out or who she told. But surely Mexico knows her experiment is still out there now and wants it back."

But Isabella was calm. "Then it will not be long before people will start looking for Phineas too. I have a plan. Are you ready?"

"Ready steady."

"Letting our governments know we lost our perfection was not an option because then they would be even more inclined to test us against each other. There was then definite reason to believe one of us was better than the other, and a clearer winner could have been decided. This was not an option, so faking our deaths was the only way to keep our rights to live our own lives. That you understand.

"Now, however, they are under the impression that we are both still alive and perfect as ever, blind to the fact that we have not been in years. They want us for our perfection now. The only thing to do is show them we do not have it."

"They won't want to pit you against each other again?" Gretchen suggested. "And how will you show them if that isn't the case?"

"What they do know about Phineas and I is that we are together," Isabella reminded her friend. "They saw that very clearly. Indeed, there is a way I can say for sure that will return us to the Phineas and Isabella that you know. By the end of today it will have happened. From there we can act, but there is no telling if we may ever become perfect again after that."

"So it's either stay perfect and be subjected to whatever Mexico wants to do with you," Gretchen summed, "...or get them off your back and never be perfect again? What kind of judgement do you need to make a decision like that?"

"Just the judgement I have," she responded. "There is another deciding factor to this to consider as well, I remind you. Now I must humbly request one more thing from you."

Gretchen stared, honored. "Anything."

"If you have not already, disregard the uncertainty with which I approached the subject before. Call Phineas and find out if he is the same as I. We can go from there."

"And if he asks me not to tell anyone?"

"Convince him otherwise. Tell him about Ascensión and the decision he will have to make, if he is perfect."

"Okay. I will try my best."

* * *

Phineas had only been travelling for an hour, and he was already getting suspicious looks for being the only good driver on the road. He had pulled over when his phone rang, and the ensuing conversation was not an expected one. Everything was handled fine, though - there was no obstacle he could not overcome today. He just knew he had to get to Tri-State as soon as possible, and he was already on his way.

That answers the question of whether to stay perfect or not.

Isabella was standing in the parking lot of Tri-State State and doing little more than waiting. Tonight's full moon was already on its way up through the sky, where no clouds strayed near it. On the other side the setting sun stained the infinite blue canvas with pinks and oranges. Isabella appreciated its beauty, but that did not set her apart: anyone who saw it would have.

Save for one person.

Ascensión Aguadulce was the only one of her group still associated with MOWCA, and de facto leader of her team once Graciela Guerrero betrayed it. Now she was head of her division and stubborn enough to go alone on her own missions. Word had spread of Perfeneas and Isealia's reappearance from the American government to the Mexican one to MOWCA to her, and no one fostered a greater resentment towards the two than her.

There she was, that lying fool whom everyone deemed perfect. Inside Ascensión was a burning that was not raging and uncontrollable but worse: steady and durable and stubborn as she was. Discreetly she peeked around the school building, aimed a special laser from her wristwatch communicator at the girl's head, and fired.

No reaction. Immune. She really was Isealia.

For the past ten years Ascensión had wished her alive again just for this encounter, and she left the moment she heard it was true. What happened next was in none of her fantasies, however.

"I know you're there, girl," Isealia announced in Spanish. She turned to her, and Ascensión gulped. "I know what you want from me, and I see it fair to inform you I have no intention of complying. Show yourself so we may speak as reasonable people."

The furious young woman bared her teeth instead, sprinting out towards her. Isealia used the momentum against her and grabbed her in a lock that issued no pain but allowed no movement. "Let go of me!" Ascensión screamed. "My whole life I've been bound to protecting you! You robbed me of a childhood and then died in the eyes of millions! Now everyone will know you lied in the face of billions and my only allowed purpose was to keep that from happening! Let GO!"

Isabella had seen Phineas angry before, but never as fumed as the person in her hands. The agent tried thrashing about, attempting to clamp onto her arm with her spiteful jaws. Isabella did not let her but spoke calmly.

"If Phineas and I did not do what we did," she explained, "Mexico and America would still be at war today. Casualties would number in the thousands or more. We did what we had to to save their lives. Ascensión, I did nothing to harm you. You are a successful MOWCA agent and a driven young woman - you can do and become anything you wish. I never kept you or your country from that."

Ascensión shrieked. "It's your country too and we want you back. But you took away my chances to be anything more than vengeful soldier. You are perfect! I could never be like you!"

Isabella closed her eyes. That is what this was about.

"Ascensión. Listen to me please. No one can be perfect."

"Oh yeah? Really!?"

"I have not for eleven years. I am now only because of scientific happenstance, and even so not entirely. Eleven years of being like you means I can never truly go back."

"Liar, I will hear none of it!" She kicked wildly as much as she could.

Isabella tried reason. "If I was perfect, would I be a liar?"

"When it benefits you!"

She sighed patiently. "Your definition of perfection needs revision."

With that, she let the woman go. Exhausted, Ascensión whipped around to face her and made herself as intimidating as possible. But Isealia was not fazed. Why should she be?

"I will revise nothing," Ascensión spit. "If what you say is true, show me you're not perfect! Show me you're just like everyone else so I can feel even worse about not being _you_!"

At that moment Ascensión noticed the guard approach. She hissed at him. Isealia explained the situation rapidly and gave chase when Ascensión tried to use this opportunity to flee. Two dashed after one and it was sooner than later when the guard grabbed her by the shoulders and everyone was able to breathe.

The agent tried to grab her wrist communicator for one of its contained weapons, but Isealia had somehow slipped that off before without her noticing.

Isabella knew that Phineas was now perfect again too from another conversation with Gretchen. So it stood to reason that his timing would be perfect in addition.

He parked near the building and spotted them quickly. "Isabella!"

In an instant they had their arms around each other, disregarding all else. He moved his hands to her face and they shared their first and only kiss as the perfect humans Perfeneas and Isealia.

The guard's mouth was agape at the two white-clad students. Ascensión's mouth was a straight line.

The two did not move for a full five seconds, but during those five seconds they felt the change they knew was coming. Each softened, relaxing into each other's arms. They broke apart and invested a second in appraising the other's eyes. Yep, still beautiful.

Even though they were no longer perfect.

They turned to Ascensión. "Now you don't have to worry about perfection ever again," Isabella offered, switching back to Spanish. "We all have our moments. Ours was longer than most people's, but as a fortune of our origins and not a result of our hard work. Maybe it was unfair for you. But take inspiration from this, okay? No one can be perfect, but anyone can be exceptional. Even you!"

"I still hate you."

"Touché." Isabella shrugged.

The guard closed his mouth and took her away.

* * *

Phineas's dorm was all packed and the young adults wearing color again within a few hours. "Now come on," Isabella said, grabbing his hand. "The surprise I wanted to tell you about."

She led him outside to a courtyard behind their dorm. At its center was a maple tree growing sturdily on green grass with the finest of care. Not as large as the one at home, but strikingly familiar.

"Are you kidding?" Phineas was ecstatic. "This is so great. It's just like home."

"It will be our home for the next few years," she reminded him. "I just had to make sure there was a good enough backyard."

"I love it."

There was silence as they took it all in. It was rather dark now, the scene lit by fireflies and the odd lamp and the unrestrained full moon.

"So the governments are probably still after us," Phineas said. It had to be addressed.

"Definitely. What will they want us to do?"

"Fight each other?"

"Destroy each other?"

"Who can say?"

They did not answer that. Perfeneas and Isealia could say, and they both knew it.

"Isn't there something we can do?"

They both knew the answer to this, too. Fortunately, Phineas was prepared for exactly that.

"Last day of summer for the rest of our lives, huh?"

"Oh, yeah." She paused. "Phineas, now I'm going to cry."

"Oh, don't," he pleaded. "Baljeet put it better than I ever could have: last day of summer means first day of school!"

"What does that mean?"

"It means we have so much more to look forward to now. Maybe not in Danville, maybe not with Ferb and our friends. But at least with each other, got that?"

She nodded.

"That's why we were able to change back just now. You know that, right? Emotional desire brought us down. Emotional fulfillment brought us up. Emotional expansion just brought us back to who we are - and who we will be together."

Isabella was smiling, but she insisted, "Okay, now I really am going to start crying."

"No, listen - what I'm trying to say is, what I want the last thing I do on the last day of summer in my life to be is to ask you a question."

He took today's project, tailored entirely by Perfeneas, out of his pocket and opened it up.

He took a knee.

"Will you marry me?"

Happy did not begin to describe what Isabella was feeling, nor did perfect the moment. "Yes!" She shouted immediately. "Yes, I will!"

* * *

 **...What'd you think? Too corny? Too angsty? Too unbelievable? Too short? Reviews are the way to say these things. ;)**

 **(Just as a refresher if you were wondering, Ascensión was Adyson's Mexican counterpart. Not really the same personality at all.)**

 **Thanks for reading and all the support you gave the first two books, because this is definitely the last. Carpe Diem!**


End file.
